The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A typical automatic transmission includes a hydraulic control system that, among other functions, is employed to actuate a plurality of torque transmitting devices. These torque transmitting devices may be, for example, friction clutches and brakes. The conventional hydraulic control system typically includes a main pump that provides a pressurized fluid, such as oil, to a plurality of valves and solenoids within a valve body. The main pump is driven by the engine of the motor vehicle. The valves and solenoids are operable to direct the pressurized hydraulic fluid through a hydraulic fluid circuit to the plurality of torque transmitting devices within the transmission. The pressurized hydraulic fluid delivered to the torque transmitting devices is used to engage or disengage the devices in order to obtain different gear ratios.
In certain hydraulic control systems an accumulator is used to augment or in some cases replace the pump as the source of pressurized hydraulic fluid. Accordingly, the charge state of the accumulator is critical to properly controlling the transmission. While pressure sensors may be employed to determine the pressure of the hydraulic fluid within the accumulator, and therefore its charge state, there is room in the art for a method of determining the charge state of an accumulator that minimizes the use of additional components and sensors.